A yield strength model for the Al-Mg-Si-Cu alloy AA6111

A yield strength model is developed for the Al-Mg-Si-Cu alloy AA6111. The evolution of the strength of precipitates, as obstacles to dislocation motion, during various stages of aging is modeled according to the theories for strengthening mechanisms, as well as the microstructural and mechanical behavior of the alloy. The precipitation hardening component of yield strength is modeled for conditions where precipitates act as either strong or weak obstacles. The dislocation breaking angles for various stages of aging at 180 degreesC is estimated and the applicability of both strong and weak obstacle models examined. It is found that although the weak obstacle model could be a better choice for describing the very early aging stages and/or the low temperature processes, the entire aging period in the temperature range of 160-220 degreesC is well described by applying the strong obstacle model. The modeling results are related to the microstructural evolution in this alloy system. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.